Place the cubed pork in a bowl. Mix together the orange zest, paprika, red pepper, mint, salt and black pepper. Toss with the pork to coat well. Cover and chill for at least 2 hours.
In a large heavy pan heat 1/4 cupof the oil over medium-high. Add the pork and cook, stirring until browned. Remove to a side dish. Add the remaining oil to the pan. Stir in the onions and leeks and cook, stirring, until they are very tender...about 10 minutes. Return the pork to the pan and pour over the wine. Cover tightly, reduce heat to low, and simmer for 1 1/2 hours or until the pork is fork tender.
Taste and adjust the seasonings.
Garnish with coarse orange zest and mint sprigs.